The present application claims priority under 35 USC 119 to Japanese Patent Application No. 2001-200908 filed on Jul. 2, 2001 the entire contents thereof is hereby incorporated by reference.
1. Field of the Invention
This invention relates to an exhaust structure for a jet propulsion watercraft wherein a water jet propeller is provided in a pump room of a watercraft body and an exhaust pipe is connected to the pump room so that exhaust gas of an engine is exhausted into the pump room.
2. Description of Background Art
A jet propulsion watercraft is a watercraft wherein a water jet pump is attached to a rear portion of a watercraft body and is driven by an engine to take in water from the watercraft bottom. The water taken in is expelled rearwardly to propel the watercraft.
A jet propulsion watercraft is disclosed, for example, in Japanese Patent Laid-Open No. 2000-282840 entitled xe2x80x9cExhaust Structure for a Jet Propulsion Watercraft.xe2x80x9d The official gazette discloses a device for reducing the exhaust noise generated from a jet propulsion watercraft. According to this technique, a resonator for sound deadening is provided for an exhaust pipe connected to an engine, and the exhaust noise is caused to resonate by the resonator to deaden the exhaust noise so that a reduction in the exhaust noise can be achieved.
Incidentally, in a jet propulsion watercraft, in order to prevent water from entering the engine side from an exhaust opening of an exhaust pipe, it is necessary to form part of the exhaust pipe in a substantially U-shaped. By forming part of the exhaust pipe in a substantially U-shape, the length of the exhaust pipe becomes comparatively long. In addition, in order to allow for resonation with the exhaust noise of the elongated exhaust pipe, it is necessary to set the length of the resonator comparatively long in accordance with the length of the exhaust pipe.
Accordingly, in order to attach the long resonator in the inside of the watercraft body, it is necessary to assure a sufficient accommodation space in the inside of the watercraft body.
However, the inside space of the watercraft body is limited, and in order to assure a comparatively great accommodation space for a resonator in the limited space, it is necessary to sufficiently examine the layout of various watercraft accessories to be attached in the inside of the watercraft body.
Therefore, in order to assure an accommodation space for a resonator, a comparatively long period of time for examination is required.
Further, when a resonator is formed from a comparatively long member, it is difficult to handle the resonator. This tendency remarkably appears particularly in such a limited space as the space in the inside of a watercraft body. Upon attachment of such a long resonator, in order to assure a high assembly operability of the resonator, some skill is required.
Meanwhile, as a countermeasure for the reduction of exhaust noise, a countermeasure of blocking exhaust noise to reduce the noise or the like may be used in addition to the deadening countermeasure by means of a resonator. However, it is considered that such other reduction countermeasures as blocking require a complicated configuration from the point of view of the structure of a jet propulsion watercraft and therefore have not been placed into practical use.
Therefore, it has been demanded to place into practical use a technique which can simply reduce exhaust noise of a jet propulsion watercraft.
Therefore, the object of the present invention resides in the provision of an exhaust structure for a jet propulsion watercraft which can simply achieve a reduction of the exhaust noise.
In order to solve the subject described above, according to the present invention, an exhaust structure for a jet propulsion watercraft is provided wherein a water jet propeller is positioned in a pump room of a watercraft body and an engine for driving is connected to the water jet propeller. An exhaust opening of an exhaust pipe attached to the engine is exposed to a pump room and a resonator for sound deadening is provided for the exhaust pipe. The resonator is bent in a meandering state such that bent portions thereof are positioned adjacent to each other so that the entire resonator has a substantially flat plate-like configuration.
The resonator is bent in a meandering state such that bent portions thereof are positioned adjacent to each other so that the entire resonator has a substantially flat plate-like configuration. Since compact formation of the resonator can be achieved through the formation of the entire resonator in a flat plate-like configuration, the resonator can be disposed in a comparatively small accommodation space.
Further, since the resonator can be formed compact, handling of the resonator can be simplified. Therefore, an attaching operation of the resonator can be simply performed without any skill.
Furthermore, since the resonator is bent in a meandering state, even if water should try to enter the resonator from the exhaust pipe side, the water cannot be admitted readily into the inside of the resonator when compared with another resonator which extends linearly.
According to the present invention, the exhaust structure for a jet propulsion watercraft includes a resonator having a flat plate-like configuration extending along a wall face of the watercraft body.
Here, generally a surplus space does not remain in the inside of a watercraft body because various watercraft accessories are attached. However, a space often remains in the proximity of a wall face of the watercraft body.
Thus, in the present invention, the resonator having the flat plate-like configuration is disposed such that it extends along a wall face of the watercraft body. Therefore, since a space remaining in the inside of the watercraft body can be utilized to attach the resonator, the resonator can be further simply attached.
According to the present invention, the exhaust structure for a jet propulsion watercraft includes a wall face of the watercraft body along which the resonator extends is a ceiling wall of the pump room, and an exhaust opening of a communicating pipe extending through the ceiling wall is communicated with the resonator extending along the ceiling wall.
The pump room is outside the watercraft body, and the resonator can be attached to the outside of the watercraft body by laying the resonator along the ceiling wall of the pump room. In addition, a space around the ceiling wall of the pump room remains as a dead space. Therefore, by laying the resonator along the ceiling wall of the pump room, the remaining dead space may be utilized to attach the resonator.
Further, since the resonator is attached to the outside of the watercraft body, there is no need to assure the accommodation space for accommodating the resonator in the inside of the watercraft body.
By laying the resonator along the ceiling wall of the pump room in this manner, the resonator can be further simply attached.
According to the present invention, the exhaust structure for a jet propulsion watercraft includes a water jet propeller and a reverse basket that are accommodated in the pump room. A sound insulating member is provided for both or one of the water jet propellers and the reverse baskets such that the pump chamber is closed.
Here, since the exhaust opening of the exhaust pipe is exposed to the pump room, exhaust gas is exhausted into the atmospheric air through the pump room. Therefore, it is a possible idea to insulate exhaust sound by closing up the pump chamber. Thus, in the present invention, exhaust sound is insulated by closing up the pump chamber with the sound insulating member.
It is to be noted that the pump room is outside the watercraft body, and the space of the pump room remains as a dead space. By making the most of the dead space, the insulating member can be simply attached.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.